The present invention relates to a recording apparatus, such as a copying machine or a printer, for recording information. More particularly, it relates to a control of an image fixing condition or power in a recording apparatus having a plurality of recording material feeding modes.
A copying apparatus or printer has been made placticable wherein an image can be formed on various types of recording materials. As for such recording materials, a resin sheet and thick paper as well as letter paper and regular sheets are ordinarily used. It is important to effect the fixing operation on any of those recording materials in a stable and uniform manner. Therefore, in order to meet all of those materials, it is usual to set the fixing power or condition (the pressure and the temperature in heat-fixing; and the pressure or the speed of transportation in pressure-fixing) to the maximum.
However, under such a severe fixing conditions to meet the wide range of the recording materials, a printer which is often kept in the standby state for a long time, involves a serious problem, for example, rollers are deformed because of the high pressure and the temperature rise in the fixing device. This can result in the necessity of exchanging expensive parts or rollers, long before the service life determined solely by the ordinary use thereof is reached. In addition, in order to effect the image fixing on a usual recording material (having the thickness of several microns--200 microns, that is, relatively thin) in a stable and satisfactory manner, the fixing conditions require the high temperature and pressure, but those conditions create curl, if a sheet of paper having not more than 80 g weight is used. Furthermore, if a transmitted-light detecting means or a paper thickness detecting means is used for the purpose of distinguishing the recording material having the thickness of several microns--200 microns and the thick recording materials having the thickness more than 200 microns, erroneous detection can often occur, resulting in extraordinary toner off-set, curl, twining of the paper around the roller, paper jamming and so on. The detecting means used for those purposes are usually not durable in long time use, since malfunction can easily occur if paper dust or toner particles are attached thereto. For those reasons, they are expensive and not practical.